Vitexin protects melanocytes from oxidative stress via activating MAPK-Nrf2/ARE pathway.

INTRODUCTION: Vitiligo is the most common type of depigmented skin disease. Cellular oxidative stress caused by reactive oxygen species (ROS) has been implicated in the pathogenesis of vitiligo. Nuclear factor E2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway plays an important role in melanocytes against hydrogen peroxide (H2O2) induced oxidative stress. In addition, vitexin may protect vitiligo by inhibiting oxidative stress and inflammation. OBJECTIVE: In the present study, we aimed to investigate the antioxidant effect of vitexin-activated mitogen-activated protein kinase (MAPK)-Nrf2/ARE axis in vitiligo. METHODS: MTT assay identified cell viability of human melanocyte PIG1. Cell apoptosis was evaluated by flow cytometry. Gene and protein expression levels were analyzed by quantitative real-time PCR (qPCR) and Western blotting. Enzyme-linked immunosorbent assay (ELISA) was used to detect the expressions of inflammatory factors and ROS production. RESULTS: Vitexin inhibited H2O2-induced melanocyte apoptosis and promoted cell proliferation. Moreover, vitexin decreased expression of interleukin-1ß (IL-1ß), IL-17A, and ROS in melanocytes induced by H2O2. Subsequently, activation of MAPK-Nrf2/ARE signaling was readily induced by vitexin treatment, as evidenced by the upregulation of antioxidant genes including heme oxygenase 1 (HO-1) and superoxide dismutase (SOD). Knockdown of Nrf2 reversed the protective effect of vitexin on H2O2-induced melanocytes. And, knockdown of Nrf2 increased the expression of IL-1ß, IL-17A and ROS, and reduced HO-1 and SOD expression. CONCLUSIONS: Vitexin protected melanocytes from oxidative stress by activating MAPK-Nrf2/ARE signaling pathway. Our results suggested that the role of the Nrf2/ARE axis in the antioxidant defense of melanocytes, and the potential therapeutic strategy for vitiligo.

[Effects of different straw recycling and tillage methods on soil respiration and microbial activity].

To explore the effects of different tillage methods and straw recycling on soil respiration and microbial activity in summer maize field during the winter wheat and summer maize double cropping system, substrate induced respiration method and CO2 release method were used to determine soil microbial biomass carbon, microbial activity, soil respiration, and microbial respiratory quotient. The experiment included 3 tillage methods during the winter wheat growing season, i.e., no-tillage, subsoiling and conventional tillage. Each tillage method was companied with 2 straw management patterns, i.e., straw recycling and no straw. The results indicated that the conservation tillage methods and straw recycling mainly affected 0-10 cm soil layer. Straw recycling could significantly improve the microbial biomass carbon and microbial activity, while decrease microbial respiratory quotient. Straw recycling could improve the soil respiration at both seedling stage and anthesis, however, it could reduce the soil respiration at filling stage, wax ripeness, and harvest stage. Under the same straw application, compared with conventional tillage, the soil respiration and microbial respiratory quotient in both subsoiling and no-tillage were reduced, while the microbial biomass carbon and microbial activity were increased. During the summer maize growing season, soil microbial biomass carbon and microbial activity were increased in straw returning with conservation tillage, while the respiratory quotient was reduced. In 0-10 cm soil layer, compared with conventional tillage, straw recycling with subsoiling and no-tillage significantly increased soil microbial biomass carbon by 95.8% and 74.3%, and increased soil microbial activity by 97.1% and 74.2%, respectively.